async function fn(){
	const promise = new Promise(resolve => {
		setTimeout(()=>{
			resolve('Hello World');
		},1000);
	});
	console.log("test await");
	let res = await promise;	//	wait util promise resloved会阻塞
	
	console.log("1:",res);	
	return res;
}

fn().then(data => console.log("2:",data)); // 返回的是一个Promise
console.log("3")

/**输出
    test await
	3
    1: Hello World  // 等待1s后才输出
    2: Hello World
*/